1. Field of the Invention
This invention relates to a vehicle steering control system.
2. Description of the Related Art
Various technologies have recently been proposed for using a CCD (Charge-Coupled Device) camera or the like mounted on a vehicle, which takes an image of the surface of an expressway or any other road on which the vehicle is traveling and detects white lines (lines painted on the road and defining a lane boundary) from the obtained image and based on this, controlling steering assist torque of the vehicle such that the vehicle runs along the lane.
By providing steering assistance while preventing vehicle lane wandering, these technologies greatly reduce the burden on the vehicle operator. However, since the vehicle operator sometimes tends to depend on this steering assistance control excessively, the assignee proposed, in Japanese Laid-Open Patent Application No. Hei 11 (1999)-78953, detecting the steering torque inputted by the vehicle operator and based on the detected steering torque, determining whether the vehicle operator has the intention to drive the vehicle by himself. Similar techniques have been taught, in Japanese Laid-Open Patent Application Nos. Hei 8 (1996)-249600 and Hei 9 (1997)-91569, in which unusual driving or the degree of awakening of the vehicle operator is detected to determine the vehicle operator's intention to drive the vehicle by himself.
However, the techniques proposed by these prior art references are not always satisfactory in the accuracy of the determination of the intention of the vehicle operator to drive the vehicle and needs to be improved.